1. Field of the Invention
The present invention relates to a method of producing spherical products such as glass balls.
2. Discussion of the Background
Glass balls are prepared by melting particles of glass by heat, forming the molten glass into spherical products through the action of surface tension and cooling the spherical products. In this case, in order to prevent thus obtained glass balls from melt-bonding to each other, various proposals have been made. For instance, the glass particles are mixed with carbon powder and the mixture is heated so that the disadvantage of a mutual melt-bonding phenomenon can be avoided. However, the conventional techniques have the problems as follows.
(1) Operations are troublesome and productivity is low.
(2) The size of the spherical glass products is determined by the size of the glass particles used. However, it is difficult to obtain the glass particles having a size correctly in a predetermined range. For this reason, operations such as classification or screening are needed to obtain the spherical glass products having a predetermined size. As a result, the yield may be reduced.
As other proposals, there are a method wherein a hot gas is blown through molten glass streams at a high speed to break the glass streams so that the broken glass streams are formed into spherical bodies by the action of surface tension (Japanese Examined Patent Publication No. 20713/1967 and Japanese Unexamined Patent Publication No. 24596/1967) and a method wherein molten glass is formed into a thin film, a hot gas is blown to the thin film molten glass at a high speed to break the same, whereby the broken pieces of molten glass are formed into spherical products by the action of surface tension (Japanese Examined Patent Publication No. 27086/1974). However, it is difficult to obtain spherical glass products having an extremely small diameter and having a uniform size.
Japanese Unexamined Patent Publication No. 27086/1974 discloses that molten glass is dropwisely discharged from a rotatable cylinder having fine gaps. However, this method is poor in productivity and it can not be employed as an industrial method.
Japanese Examined Patent Publication No. 27086/1974 discloses a method of producing spherical glass products by using a rotatable body which is provided with fine orifices through which molten glass is discharged dropwisely. However, when spherical glass products having a smaller diameter are to be produced, it is necessary to reduce the size of fine orifices in correspondence to the diameter of the glass balls. Accordingly, this method can not be employed as an industrial method.